The compound 6,11-dihydro-11-(1-methyl-4-piperidinylidene)-5H-imidazo[2,1-b][3]benzazepine-3-carboxaldehyde, which is known as Alcaftadine (INN), and its corresponding salts are H1 histamine receptor antagonists indicated for the prevention of itching associated with allergic conjunctivitis and is sold commercially as an ophthalmic solution containing Alcaftadine (0.25%) under the trade name Lastacaft.
EP 0 588 858 describes the preparation of Alcaftadine for the first time through the process:

It is evident that a number of steps are needed in EP 0 588 858 to arrive at the intermediate of formula 7 (free base) from the starting compound of formula 1 with a relatively low yield. Furthermore, the introduction in the intermediate of formula 7 (free base) of the hydroxymethyl substituent and subsequent oxidation to arrive at Alcaftadine requires a cumbersome, low-yield protection and de-protection process, using an ethylcarboxylate protecting group.
In addition, the introduction of the hydroxymethyl group requires stirring with 22 equivalents of formaldehyde for at least 1 week according to example 20a) of EP 0 588 858. Long reaction times furthermore increase the risk of obtaining the dihydroxymethyl impurity (example 20b)).
There exists, therefore, the need to develop an improved process for obtaining Alcaftadine and salts thereof, which overcomes some or all of the problems associated with known methods from the state of the art. More particularly, there exists the need for a process for obtaining Alcaftadine and pharmaceutically acceptable salts thereof, which results in a higher yield and/or having fewer reaction steps.